This invention relates to a self-cleaning filter apparatus, and more particularly to a rotary sweep arm for a self-cleaning filter apparatus.
Rotary sweep arms having vaccum or suction heads for cleaning screen-covered ports are well-known in the art, as illustrated in the Noland U.S. Pat. No. 3,377,780, the Streun U.S. Pat. No. 2,601,704, British Pat. No. 1,155 dated Jan. 16, 1906 and in British Pat. No. 343,085, dated Nov. 13, 1929.
The Noland patent discloses that it is old to employ a rotary vacuum sweep in a self-cleaning filter apparatus for a grain dryer.
Nevertheless, none of the rotary sweep arms disclosed in any of the above patents are provided with any means for creating a uniform vacuum along the radial extent of the nozzle of the sweep arm. In sweep arms of uniform dimension, greater suction is more likely to be applied closer to the rotary axis, with the vacuum decreasing radially outward from the rotary axis. Accordingly, the cleaning effect will be greater closer to the center of the rotary sweep and least efficient at the radial tips of the sweep arm.